Moscow, August 1 (RFE/RL) -- Tens of thousands of coal miners in Russia's southern Rostov region joined a strike over unpaid back wages today, in solidarity with their striking co-workers in Russia's Far East.

Ruben Badalov, deputy head of Russia's Independent Trade Union of Coal Industry Workers, said 17 out of 24 mines in Rostov had gone on strike. Itar-Tass said this amounted to over 70,000 miners, in addition to the 13,000 miners already striking in Russia's Far East.

Mine workers in Rostov have not received any pay for the last four months. Badalov said the total amount owed to miners in back wages across Russia amounted to two trillion rubles ($390 million).

Some of that money is owed by the federal government, but most of it is owed by energy users who have not paid their bills to the coal mines.

"There is a very high probability of an all-Russian strike," if miners are not paid, said Badalov.